Pressing devices are used for various purposes such as, for example, for crimping cable lugs on electrical cables, but also for cutting cables or for punching holes into sheet metal constructions. In order to realize these different applications in one machine, a system for interchanging a head provided with the respective tool is required. For the sake of simplicity, the different attachable heads are simply referred to as interchangeable heads below. The same pressing device can be easily and quickly adapted to other applications on demand with the aid of different interchangeable heads.
However, one particular problem of pressing devices with interchangeable heads are the longitudinal forces to be transmitted, i.e. the compressive forces or pressures generated by the pressing devices, which the coupling mechanism has to withstand. In this context, conventional longitudinal forces lie in the range, for example, between 24 kN and 130 kN.
The aim therefore is to develop a coupling mechanism that can be easily and quickly handled, but nevertheless also operates reliably under very high longitudinal forces.
For example, document US 2013/0264085 A1 discloses a coupling for connecting an interchangeable tool head to a machine part of a pressing device, in which high longitudinal forces consequently also act upon the coupling mechanism.
US 2013/0264085 A1 furthermore discloses a cylindrical shaft section on the part of the pressing device on the machined side, wherein the shaft section can be accommodated in a corresponding receptacle region of an interchangeable tool head and is axially displaceable therein. A plurality of interlocking lugs is arranged in the receptacle region of the interchangeable tool head, as well as on the circumferential surface of the shaft section. A closed position can be adjusted by rotating the interchangeable tool head and thereby lining up the interlocking lugs in the receptacle region with the interlocking lugs on the shaft section. In the closed position, the interchangeable tool head can be prevented from separating from the machine part. An open position, in which the interchangeable tool head can be separated from the machine part, can be adjusted in at least one angular position by rotating the interchangeable tool head. In other words, a bayonet joint is formed between the interchangeable tool head and the machine part.
In the coupling known from US 2013/0264085 A1, the shaft section consists of two parts, namely of a hollow cylinder and a piston that can be displaced therein, wherein a spring located in the shaft section causes the piston to retract into the hollow cylinder when hydraulic pressure is released.
Due to the two-part construction of its shaft section, the coupling in the form of a bayonet joint known from US 2013/0264085 A1 has a comparatively complicated design.
There basically is an ongoing demand to additionally improve the operational reliability of the coupling mechanism in pressing devices with high longitudinal forces.